OG 39 - as

39. For members of the seventeenth-century Ashanti nation in Africa, animal-hide shields with wooden frames were essential items of military equipment, a method to protect warriors against enemy arrows and spears.
(A) a method to protect
(B) as a method protecting
(C) protecting
(D) as a protection of
(E) to protect
Choice C is best because the participle protecting begins a phrase that explains what the shields did. Choices A and B awkwardly use the singular word method to refer to items of military equipment rather than to the use of such items. Also, a method of protecting would be more idiomatic than a method to protect in A or a method protecting in B. In B and D, as is incorrect; also, a protection in D has no noun for which it can logically substitute. Choice E is incomplete; used to protect would have been acceptable.

Would you please tell me why 'as' in B and D is incorrect?

Thanks

如果要加as,前面好像少了点东西,如used as...,要不不知道介词短语放这做何成分.另外,感觉也没必要,本来a method 和a protection修饰 shields就已经有作为...的意思了.罗嗦.

谢谢，我也感觉没有必要，但是OG是说这种用法错，有点不明白才问。你的看法我认为有道理。

首先， a protection in D has no noun for which it can logically substitute. 不是很能理解？

另外，对于as，刚才查了“英语语法大全”，没有发现d中的as使用有什么不对，请教大家！

最后， a method of protecting would be more idiomatic than a method to protect in A or a method protecting in B.  为什么用动名词会好些，请教！

谢谢！

怎么没有人回呢？

自己顶一下！

顶一下，我也是这个问题，为什么a method to 不行而要a method of ？？？

四楼的问题, 同问.

一位大侠的小结，十分有帮助，各位可以参考以下。

http://forum.chasedream.com/dispbbs.asp?BoardID=23&ID=48608